How do roller coasters go so fast?

Dr. Universe: How do roller coasters go so fast? How do they stay on their tracks?

–Bhayana, 10, Jacksonville, AR

Dear Bhayana,

The very first roller coaster at Coney Island amusement park cost only a nickel to ride and was a big thrill for visitors—even if it did only go 6 mph.

Those visitors would be surprised if they rode the high-speed coasters of today. It turns out roller coaster speed has a lot to do with height and the way things store energy.

You get energy from eating food, for example. You can use this energy to do work. Maybe that work is riding a bike up a big hill.

The energy helps you pedal. But if you were to pedal downhill, the experience would be really different. You might not even pedal. You could probably just coast.

Roller coasters work in a similar way, said my friend and professor Bob Lewis. Students in his computer science classes at Washington State University create roller coaster simulations as part of their work. Lewis said roller coaster speed is all a question of height.

Just like you store energy in your body, energy can be stored in the form of height. That means if you were to find the fastest roller coaster at an amusement park, chances are it would be one of the tallest.

Keep your paws and tail inside the ride at all times

Let’s say you hop on this big roller coaster, buckle up, and pull down the safety bar. As you start to go up the hill, the car is being helped by a chain or pulley. At the top, the coaster has a lot of stored energy, or potential energy.

Once the coaster starts heading downhill, it has everything it needs to carry you through the rest of the ride. Roller coasters continuously exchange potential (stored-up) energy and kinetic (motion) energy. Going up, kinetic energy is turned into potential energy. Going down, potential energy is turned into kinetic energy.

Staying on track

Now, the answer to your second question: If you look up close at a roller coaster, you’ll see that the wheels are arranged in just the right way to keep everything on track.

Often, there are three sets of two wheels. One set sits on top of the track, one sits below, and the third glides along the side of the track. When the roller coaster is going really fast, it naturally wants to travel straight.

But engineers can design the tracks to curve, or bank. It’s pretty similar to what happens when you are in the car traveling on a curved road. You feel the centrifugal force. We counteract the tendency of the car to want to go straight by tilting the road, Lewis said. The same is true with rollercoasters.

You know, you can create your own kind of roller coaster with a few simple supplies. You’ll need some foam tubes, or a some kind of tube-like material, marbles, tape, and scissors. You can find all the instructions, here. Share your mini coaster with us anytime at Dr.Universe@wsu.edu.